1. Field of the Invention
The present invention relates to an X-ray computer tomography (CT) apparatus for dentistry or a jaw/face region. In particular, the present invention relates to an X-ray CT apparatus capable of performing local X-ray CT on a certain tooth or the like as an region of interest in dentistry or the jaw/face region, and performing panoramic X-ray imaging on a curved cross section of a dental arch, a jaw joint, and the like.
2. Description of the Related Art
The Japanese Patent Publication No. 10-225455 (A) discloses an X-ray CT apparatus for dental diagnosis. This X-ray CT apparatus is one having a local X-ray computer tomography (hereinafter referred to as “CT”) along with a panoramic X-ray imaging mode. This X-ray CT apparatus is capable of selecting the X-ray CT mode and the panoramic X-ray imaging mode, and characterized as follows: when the X-ray CT mode is selected, a rotational central axis is fixed onto a central axis of an region of interest, and when the panoramic X-ray imaging mode is selected, a rotational arm having an X-ray generator and an X-ray detector is rotationally moved while the rotational central axis moves along a locus for the panoramic X-ray imaging during imaging.
The Japanese Patent No. 3540916 (B) discloses a three-dimensional X-ray CT scanner, having in a hollow rotating body an X-ray generator and an X-ray detector which are opposed to each other with a horizontal central axis (rotational axis) provided therebetween. In this apparatus, while these X-ray generator and X-ray detector are rotated with respect to an imaging object positioned inside the rotating body, X-rays having been radiated from the X-ray generator and transmitted through the imaging object are detected in the X-ray detector, and using the X-ray image detected in the X-ray detector, a three-dimensional tomographic image can be reconstructed, so that an offset scan/CT method by which a three-dimensional CT image in a larger range than a visual field angle of a two-dimensional X-ray detector is obtained in addition to a so-called normal scan/CT method by which a CT image is obtained by irradiating the whole of the imaging object with X-rays.
This offset scan/CT method has the advantage of being capable of performing X-ray CT in a larger range than the visual field angle of the two-dimensional X-ray detector since part of the region of interest of the imaging object may be irradiated with X-rays at each time point during imaging, as compared with the normal scan/CT method of constantly irradiating the whole of the region of interest of the imaging object with X-rays at each time point during imaging.